1. Field of the Invention
The present invention relates to castors for associating with any type of article that is movable in the broad sense in order to make the article easier to move over a floor surface, e.g. castors that find an application in moving hospital equipment and furniture, beds, tables, wheelchairs, carriages, walkers, and also castors for moving suitcases, baggage, or the like.
Such a castor essentially comprises at least one wheel, generally two wheels, a casing for supporting and protecting the wheels, and a pivot that provides a connection between the casing and the movable article.
Its structure needs to be designed so as to make it easy to move the movable article with which it is associated in any direction.
For this purpose, it generally comprises two parallel-mounted wheels, means for enabling those two wheels to rotate about a horizontal shaft relative to the casing in order to run on the floor so as to move the movable article in rectilinear translation, and also means to enable the casing to be connected to the movable article so as to be capable of pivoting relative to the article about an axis that is substantially vertical and thus enable the castor to take up any direction relative to the article so as to make it easy to steer the article around curves.
2. Description of the Related Art
When such castors are used, e.g. in a hospital or the like, for the purpose of moving a piece of furniture carrying a patient or items such as instruments, various fluids, and other medical equipment that is relatively fragile, it is preferable to avoid subjecting the patient or those items to shocks that are too great, e.g. when the movable article is moved over a floor surface that presents discontinuities such as the thresholds of certain doors, e.g. fire-break doors or the like. It is therefore advantageous for the castors to be capable of absorbing such shocks, at least in part. The same applies to baggage or the like associated with such castors.
It is also preferable for such castors to avoid making too much noise when running on the floor surface, in particular in a hospital or the like in order to keep it quiet for hospital patients, or in any other location when moving suitcases, baggage, or the like.
A castor with a shock absorber is already known, such as that described and shown in DE 2 937 571. That castor essentially comprises a casing constituted by a first portion and a second portion that are made respectively of two materials of different flexibility, the second portion, which is made of the material having the greater flexibility, being the portion that constitutes the housing for the pivot and thus the bearing for the shaft of the wheel. This second portion is made of rubber and is fastened to the first by means of a pin, and it therefore cannot be molded with the first portion. Furthermore, since the second portion is made of a material that is very flexible and that is directly in contact with the shaft of the wheel, it is very difficult for the material to support the shaft, and the shaft is therefore easily made to oscillate e.g. when the castor runs over the floor and encounters roughnesses or the like. In addition, the second portion is subjected to wear that is very fast.